Fifth wheel hitches have been used for decades to tow a trailer behind a vehicle. Conventional fifth wheel hitches typically include a support frame for mounting the hitch to the towing vehicle, such as, for example, to a bed of a pickup truck and a head assembly which includes the mechanism for attaching the hitch assembly to a king pin of the fifth wheel trailer.
The support frame of conventional fifth wheel hitches often includes a pair of base rails that are bolted to the bed and/or frame of the truck, side brackets that are releasably mounted to the base rails and a head support mounted to the side brackets. The head assembly is mounted to the head support by means of a trunnion arrangement allowing for pivotal fore-and-aft movement relative to the side brackets.
For fifth wheel hitches designed to couple to a king pin-type fifth wheel, the head assembly includes a jaw assembly operable by means of a control handle. The jaw assembly is specifically adapted to releasably engage and hold the kingpin of the trailer.
Conventional fifth wheel trailer hitches are typically centered over the axles of the rear wheels of a towing vehicle so as to place the tongue-weight of the vehicle over the rear tires. While this results in a desired weight positioning of the trailer relative to the towing vehicle for traveling at highway speeds, it also often positions the front of the trailer relatively close to the cab of the towing vehicle. When maneuvering at low speeds, the turning radius of the trailer and towing vehicle will be limited by the proximately of the front of the trailer to the cab of the towing vehicle. Thus, the closeness of the clearance between the towing vehicle and the trailer can significantly limit the maneuverability of the towing vehicle and trailer when tight corning is desired.
In order to address the disadvantage in maneuvering a trailer using conventional fifth wheel trailer hitches, various attempts at adjustable fifth wheel hitches have been made. It has been found that by temporarily moving the hitch assembly rearward in the towing vehicle, clearance between the towing vehicle and the trailer is increased, thereby allowing for greater maneuverability of the towing vehicle and trailer.
One such hitch is disclosed in U.S. Pat. No. 6,247,270 to Linger et al. The hitch described in Linger et al. is typical in the art of an adjustable fifth wheel hitches that can move between first and second positions. Linger et al. includes a pair of spaced guide rails upon which a pair of rollers are positioned. The rollers are coupled to a pair of upright assemblies that support the head assembly. Upon movement of the rollers relative to the guide rails, the head can move between first and second positions. The result is a hitch that moves linearly between the first and second positions. The hitch is actuated between the first and second positions by driving the towing vehicle forward to move the head assembly to a rearward position and driving the towing vehicle in reverse to move the head assembly to a forward position. The head assembly can be locked in either the forward or rearward positions relative to the guide rails.
A principle problem with such linearly moving, adjustable hitch assemblies is the ability of such adjustable hitches to bind during movement between the first and second positions. As a significant load may be present on the hitch (both vertically and horizontally), if the trailer is not positioned directly behind the towing vehicle when adjustment of the hitch is being made, the roller assemblies can easily bind relative to the guide rails as one roller assembly moves ahead or behind the other roller assembly. Such binding can result in damage to the hitch assembly and/or the inability to move the hitch assembly to a second position where it can be locked to prevent further movement of the head assembly relative to the towing vehicle.
Accordingly, there exists a need in the relevant art to provide an adjustable fifth wheel hitch that is capable of selectively moving the head assembly of the hitch rearward for greater maneuverability at low speeds and forward for greater stability when traveling at high speeds in a smooth, non-binding manner.
Furthermore, there exists a need in the relevant art to provide an adjustable fifth wheel hitch that is capable of overcoming the disadvantages of the prior art.
These and other advantages will become apparent from a reading of the following summary of the invention and description of the preferred embodiments in accordance with the principles of the present invention.